α-Synuclein is a presynaptic protein whose aberrant aggregation causes neurodegeneration in Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and several variants of Alzheimer’s disease (Singleton et al., 2003; Lee and Trojanowski, 2006; Cookson and van der Brug, 2008; Ingelsson, 2016). This evidence concerns the gene SNCA and Lewy body dementia.